Torch size doesn't have much to do with output, but it can have to do with comfort. My MECO is a case in point. I should note that they make a longeneck accessory. In standard form it will blaze away all you want, but your hand is too close, of course one could MacGyver a handle extension for it also. I love it by the way.
Classically, most frame builders once used standard size torches. Even the small sizes now in vogue were originally designed for aircraft welding. They are called aircraft torches, and you can be sure people weren't using them for lugged airframes. In welding the torch is often horizontal where extra weight is very noticeable, and one is following a line, not just artfully throwing the heat around. These days, most people are such healthy specimens they want to use the delicate welding torches for general work, possibly with ultralite hoses. Pass the beefsteak!